Progress of Seedlings in Greenhouses

The 2023 greenhouse season is progressing, and it has been characterized by few warm days and many cool and cloudy days. Nevertheless, most greenhouses have good seed germination and seedling uniformity. Based on the greenhouses that the CTRF has visited, seedlings between farms do vary in size depending on the type of production method being used and when seeding was started.

Preventative applications of the fungicide for the control of Rhizoctonia Damping-off in greenhouses has occurred, and clipping is underway.

Some of the problems that have been reported so far include algae on media surface (float trays) and chilling injury.

Effects of  Algae on  Seedlings in Trays

Certain algae present on the surface of tray media can affect seedling emergence and establishment. Two situations are usually seen in these cases, one where the seedlings are not able to emerge through the algae and the other being where the seedlings emerge but cannot establish themselves before succumbing to the algae and dying (as shown below).

Cool and cloudy weather conditions are ideal for algae growth, and there are no chemical treatments for algae in tobacco greenhouses. Conditions that are optimum in the greenhouse for rapid seed germination and early seedling growth help seedlings to outpace the algae so that the seedlings become large enough that the algae can no longer affect them.  As seedlings grow, the canopy will close over and shade the media surface, therefore, reducing the negative effects of algae. At this time, in some greenhouses, the after-effects that algae can have on young seedlings in trays are evident and are characterized by significant stands reduction and uneven seedling growth.

Chilling Injury

Chilling injury is being observed in some greenhouses. Chilling injury is caused by exposure of the seedlings to a large variation in air temperature, such as when ventilation occurs on a very cool but sunny day or at night when the temperature outside is quite cold and the temperature drops significantly in the greenhouse because the heaters do not have enough capacity to maintain the set temperature.

The initial symptoms of chilling injury are often a bright yellow colour in the growing point of the seedling and upward cupping of the leaves, as shown in the image below.

As the seedlings become larger and the leaves grow out, some leaves become malformed, cupped, and have a distinct yellow/white discoloration. Seedlings do outgrow chilling injury without any ill-effects on the seedlings when transplanted to the field. However, when chilling injury affects the seedling growing point, the plant responds by producing lateral growing points, (suckers), which affects the quality of seedlings.

Clipping Tobacco seedlings in Greenhouses

Currently, clipping of seedlings is taking place in most greenhouses. Be on the lookout for the occurrence of Bacterial Soft Rot (also known as Blackleg), a disease that occurs in both float and dry trays greenhouses during clipping. Bacterial Soft Rot starts when leaf debris fall back onto the seedlings from the clipper, becoming a food source for the  bacteria.  Factors such as, warm temperatures, high humidity, extended periods of leaf wetness, high nitrogen levels and plant injury (by stress or wounding) contribute to  Bacterial Soft Rot spread and outbreaks in greenhouses.

Bacterial Soft Rot infects tobacco seedlings in both dry cell and float trays and has the potential to destroy large numbers of plants in a brief period of time. Initially, the bacteria colonize wounded tissues, organic matter, and debris in trays. Leaves touching the surface of a tray can become infected and the rot can spread through the petioles into the stem of the seedlings. 

Infected seedlings transplanted into the field may not become well established and may not survive. There are no control agents registered for control of Bacterial Soft Rot in tobacco greenhouses. Removal of trays with the diseased seedlings from the greenhouse and replacing them with blank trays is the best control in this situation.  Other practices for control include trying to keep leaf debris from the clipper out of the beds, not clipping when the leaves are wet, not over-fertilizing, keeping the foliage of the seedlings as dry as possible, and ventilating the greenhouse adequately to keep the humidity level down in the greenhouse.

Tobacco fields Soil fumigation

Soil fumigation in preparation for the season has started.  It is important to remember that cooler temperatures and rainy conditions that have been occurring lately may impact the performance or efficacy of the soil fumigants.

When applying fumigants, ensure that the soil temperature and soil moisture are in accordance with the label requirements/recommendations for the specific soil fumigant that is being used.  As we get closer to planting season, please note that different soil fumigants may require different time intervals between fumigation and transplanting.

Please follow the label associated with the soil fumigant that was used and refer to the product label for more information.

Post prepared and sent by Canadian Tobacco Research Foundation

Mailing Address: CTRF, P.O. Box 322, Tillsonburg, ON  N4G 4H5

Telephone: 519-842-8997

Web Address:  http://ctrf1.com

The Canadian Tobacco Research Foundation (CTRF) is seeking a Technical Research Assistant who will assist in the successful implementation of greenhouse, field, harvest, and post-harvest activities associated with the CTRF’s plant Protection, Agronomy and Breeding programs.

Please follow this link for the job description and more information related to the position.

If you are interested in applying for this position, please outline your experience and qualifications in a cover letter and resume, be prepared to provide references, and submit this information to one of the following:

Mail :

P.O. Box 322.

Tillsonburg, ON, N4G 4H5.

Email: maythem.alamery@ctrf1.com

In person :

Unit 3, 500 Highway 3.

Tillsonburg, ON, N4G 4H5.

Post prepared and sent by Canadian Tobacco Research Foundation

Mailing Address: CTRF, P.O. Box 322, Tillsonburg, ON  N4G 4H5

Telephone: 519-842-8997

Web Address:  http://ctrf1.com

The agronomic performance data for the registered varieties grown in 2022 can now be viewed on the CTRF Plant Breeding website.

The CTRF established plots of the most commonly grown flue-cured tobacco varieties in Ontario to compare performance for 2022. A two-year (2021 + 2022) and three-year (2020 + 2021 +2022) average of these varieties are also presented. If you have questions about this handout, please contact the CTRF.

Post prepared and sent by Canadian Tobacco Research Foundation

Mailing Address: CTRF, P.O. Box 322, Tillsonburg, ON  N4G 4H5

Telephone: 519-842-8997

Web Address: http://ctrf1.com

The CTRF is holding an “Open House” on Wednesday, December 14, 2022, between the hours of 8:30 a.m. and 12:00 noon.  Please stop by and look at the cured leaf samples of registered and promising varieties that will be on display.  Handouts on the performance of the registered varieties will be available.  The CTRF’s plant pathology and agronomy programs will have a display in CTRF’s lab that highlights some of the research that was conducted this year.  Click here for the program and directions.

Post prepared and sent by Canadian Tobacco Research Foundation

Mailing Address: CTRF, P.O. Box 322, Tillsonburg, ON  N4G 4H5

Telephone: 519-842-8997

Web Address: http://ctrf1.com

The majority of the crop was planted in late May and early June and crops are off to a good start, with cultivation now starting to occur. Problems observed in greenhouses this spring include chill injury, chemical injury, pH in float water, spiral roots, dry cells, and algae. In the field, there have not been many problems reported yet. However, there have been reported cases of plants showing  damage due to  environmental stresses, particularly low night temperatures  soon after transplanting. As a result, we have started to see in certain fields plants that are forming suckers.

There have been a few growers asking about tray sanitation now that transplanting is finished.  It is important to mention that unless Styrofoam trays are properly sterilized following use each year, it is not uncommon for fungi to build up in the trays and infect the plants. The CTRF has encountered Black Root Rot in Styrofoam trays over the past years when steam has not been used to disinfect them. As of today, sterilization of Styrofoam trays with steam is the only practice that will effectively control Black Root Rot. For more information on Black Root Rot and its control, please refer to the technical bulletin entitled “Tobacco Pests and Disorders in the Field – Black Root Rot” posted in the Plant Protection area of this website. Please see the technical bulletin “Tobacco Pests and Disorders in the Greenhouse-Damping Off” for more information.

Post prepared and sent by Canadian Tobacco Research Foundation

Mailing Address: CTRF, P.O. Box 322, Tillsonburg, ON  N4G 4H5

Telephone: 519-842-8997

Web Address: http://ctrf1.com

The 2022 greenhouse season is underway with a cool and cloudy start. At this time, all greenhouses have been seeded. Overall, seedling stands in greenhouses should provide adequate transplants for this year’s crop. As the seed germinates and seedlings grow, pests, tray and greenhouse conditions, fertility, and contaminations due to drifting of pesticides may arise and affect the crop.

Based on the farm calls received and the greenhouses that the CTRF has visited, seedlings between farms do vary in size depending on the type of production method being used and the time of seeding. Thus far, there have been a variety of issues occurring in the greenhouses, including dry cells, slow seed germination, uneven seed germination and seedling growth and algae formation on the surface of media interfering with seedling emergence and growth.

1-Dry cells

Styrofoam dry cells were observed in some float greenhouses when some tray cells showed dryness after floating (fig 1). The exact cause of cell dryness is not clear,  but it can be associated with debris in the soil mix or issues with soil wetting agent and filling up cells loosely. These factors may prevent water absorption and soaking of the growth media, which will result in slow seed germination. To mitigate cell dryness some growers mist the trays’ surface using a handheld hose equipped with a mist nozzle.

2- Slow seed germination

Soil media in trays is essential for seed germination since it sustains seed germination and growth soon after seeding. If the soil media conditions are not adequate to ensure proper aeration, by not filling the trays too tight or too loose, media wetness, soil and water (float trays) and overall greenhouse temperatures, slow seed germination and seedling growth will occur. Greenhouse temperature is crucial for seed germination and growth. Cooler temperatures during seed germination will extend the number of days necessary to reach maximum germination and to decrease uniformity in the size of seedlings, and after germination, they can exacerbate seedlings’ chilling injury. A temperature of 24°C or 75°F is recommended for optimal seed germination and seedling growth and a temperature of at least 15°C or 60°F or higher be maintained during the first 14 days. However, some growers will maintain at least 21°C or 70°F for the first 14 days to maximize the speed of germination and plant uniformity. After the first 14 days, good rates of seedling growth can be achieved with an overnight minimum temperature of 10°C or 50°F without any injury to plants.

3- Algae

Algae may develop on the surface of either dry or float trays, especially under cool and dim conditions. Several distinct types of algae may form on trays depending upon what types were in the substrate used to fill the trays or which types were present upon the trays from previous seasons. Blue-Green Algae are the most common algae in greenhouses, and they affect tobacco seedlings by causing oxygen levels in the media to fall, thus inhibiting root growth, and  competing with the plants for fertilizer. Two situations are usually seen in cases of algae infection, one where the seedlings are not able to emerge through the algae and the other being where the seedlings emerge but cannot establish themselves before succumbing to the algae and dying.

There are no pesticides registered for algae control in tobacco greenhouses. Algae are best managed by providing conditions as favorable as possible for seed germination and early seedling growth, so that the seedlings will establish quickly and outpace the formation of the algae on the media surface. Following good tray fertilization practices is also essential since it encourages algae growth. Therefore, fertilizer should not be added to float tray water until the plants have reached the two-leaf stage. For dry trays, fertilizer applications should not start until three weeks after seeding. As seedlings grow, the canopy will close over and shade the media surface, therefore, reducing the negative effects of algae.

Post prepared and sent by Canadian Tobacco Research Foundation

Mailing Address: CTRF, P.O. Box 322, Tillsonburg, ON  N4G 4H5

Telephone: 519-842-8997

Web Address: http://ctrf1.com

The agronomic performance data for the registered varieties grown in 2020 can now be viewed on the CTRF Plant Breeding website.

The CTRF established plots of the most commonly grown flue-cured tobacco varieties in Ontario to compare performance for 2021. A two-year (2020 + 2021) and three-year (2019 + 2020 +2021) average of these varieties are also presented. If you have questions about this handout, please contact the CTRF.

Post prepared and sent by Canadian Tobacco Research Foundation

Mailing Address: CTRF, P.O. Box 322, Tillsonburg, ON  N4G 4H5

Telephone: 519-842-8997

Web Address: http://ctrf1.com

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